n-Type Control by Sulfur Ion Implantation in Homoepitaxial Diamond Films Grown by Chemical Vapor Deposition

n-type control was achieved by sulfur-ion-implantation in homoepitaxial diamond (100) films grown by chemical vapor deposition (CVD) for the first time. Sulfur-implantation was carried out with energies of up to 400 keV at 400°C. The activation energy of the conductivity was 0.19–0.33 eV depending on the conditions of ion implantation. A junction between this layer and a boron-doped p-type layer was fabricated by combining sulfur-implantation with gas-phase boron doping during CVD. The junction exhibited clear pn junction properties. The capacitance of the junction decreased with reverse bias voltage, which confirms that the depletion region of the junction was actually extended with the reverse bias voltage.